Can't save to Flash

I’m working with the .NET MF for about a half year with the Digi
Connect ME and I’m very satisfied with it. I’m using the .NET MF 2.0
SP1, also the firmware on the module is the version .net mf 2.0 SP1.

Since some time I have big problemes with the ExtendedWeakReferences,
which I use to save data to flash.
I have a counter, which counts every restart of the Digi Connect ME
and save the current amount of restarts to Flash.
I’m doing it in exact the same way, which is described in the book
“Expert .NET Micro Framework”.
For some time it works fine, but then the EWR could not be loaded
again. There’s no chance to load the data from flash and there’s no
chance to save new data to flash, which could be loaded after the next
The only way to bring it to work, is to “Erase” the Digi Connect ME
Module with MF Deploy.
Then it works for some time, but after some time the same thing
What could be wrong?
It looks to me, like there’s no memory left in Flash, and therefore I
can’t save any new data.

Looking forward to get some help!